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<title>FatFs - f_open</title>
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<body>

<div class="para func">
<h2>f_open</h2>
<p>The f_open function creates a <em>file object</em> to be used to access the file.</p>
<pre>
FRESULT f_open (
  FIL* <span class="arg">fp</span>,           <span class="c">/* [OUT] Pointer to the file object structure */</span>
  const TCHAR* <span class="arg">path</span>, <span class="c">/* [IN] File name */</span>
  BYTE <span class="arg">mode</span>          <span class="c">/* [IN] Mode flags */</span>
);
</pre>
</div>

<div class="para arg">
<h4>Parameters</h4>
<dl class="par">
<dt>fp</dt>
<dd>Pointer to the blank file object structure.</dd>
<dt>path</dt>
<dd>Pointer to the null-terminated string that specifies the <a href="filename.html">file name</a> to open or create.</dd>
<dt>mode</dt>
<dd>Mode flags that specifies the type of access and open method for the file. It is specified by a combination of following flags.<br>
<table class="lst">
<tr><th>Value</th><th>Meaning</th></tr>
<tr><td>FA_READ</td><td>Specifies read access to the object. Data can be read from the file.</tr>
<tr><td>FA_WRITE</td><td>Specifies write access to the object. Data can be written to the file. Combine with <tt>FA_READ</tt> for read-write access.</td></tr>
<tr><td>FA_OPEN_EXISTING</td><td>Opens the file. The function fails if the file is not existing. (Default)</td></tr>
<tr><td>FA_CREATE_NEW</td><td>Creates a new file. The function fails with <tt>FR_EXIST</tt> if the file is existing.</td></tr>
<tr><td>FA_CREATE_ALWAYS</td><td>Creates a new file. If the file is existing, it will be truncated and overwritten.</td></tr>
<tr><td>FA_OPEN_ALWAYS</td><td>Opens the file if it is existing. If not, a new file will be created.</td></tr>
<tr><td>FA_OPEN_APPEND</td><td>Same as <tt>FA_OPEN_ALWAYS</tt> except the read/write pointer is set end of the file.</td></tr>
</table>
</dd>
</dl>
</div>


<div class="para ret">
<h4>Return Values</h4>
<p>
<a href="rc.html#ok">FR_OK</a>,
<a href="rc.html#de">FR_DISK_ERR</a>,
<a href="rc.html#ie">FR_INT_ERR</a>,
<a href="rc.html#nr">FR_NOT_READY</a>,
<a href="rc.html#ok">FR_NO_FILE</a>,
<a href="rc.html#np">FR_NO_PATH</a>,
<a href="rc.html#in">FR_INVALID_NAME</a>,
<a href="rc.html#dn">FR_DENIED</a>,
<a href="rc.html#ex">FR_EXIST</a>,
<a href="rc.html#io">FR_INVALID_OBJECT</a>,
<a href="rc.html#wp">FR_WRITE_PROTECTED</a>,
<a href="rc.html#id">FR_INVALID_DRIVE</a>,
<a href="rc.html#ne">FR_NOT_ENABLED</a>,
<a href="rc.html#ns">FR_NO_FILESYSTEM</a>,
<a href="rc.html#tm">FR_TIMEOUT</a>,
<a href="rc.html#lo">FR_LOCKED</a>,
<a href="rc.html#nc">FR_NOT_ENOUGH_CORE</a>,
<a href="rc.html#tf">FR_TOO_MANY_OPEN_FILES</a>
</p>
</div>


<div class="para desc">
<h4>Description</h4>
<p>Before using any file function, a work area (file system object) needs to be registered to the logical drive with <a href="mount.html"><tt>f_mount</tt></a> function. All API functions except for <tt>f_mkfs/f_fdisk</tt> function get ready to work after this procedure.</p>
<p>After <tt>f_open</tt> function succeeded, the file object is valid. The file object is used for subsequent operations to the file to identify the file. Open file must be closed prior to power down, media removal or re-mount, or the file can be collapsed. To close an open file, use <a href="close.html"><tt>f_close</tt></a> function.</p>
<p>If duplicated file open is needed, read <a href="appnote.html#dup">here</a> carefully. However duplicated open of a file with any write mode flag is always prohibited.</p>
</div>


<div class="para comp">
<h4>QuickInfo</h4>
<p>Always available. Only <tt>FA_READ</tt> and <tt>FA_OPEN_EXISTING</tt> are supported when <tt>_FS_READONLY == 1</tt>.</p>
</div>


<div class="para use">
<h4>Example</h4>
<pre>
<span class="c">/* Read a text file and display it */</span>

FATFS FatFs;   <span class="c">/* Work area (file system object) for logical drive */</span>

int main (void)
{
    FIL fil;       <span class="c">/* File object */</span>
    char line[82]; <span class="c">/* Line buffer */</span>
    FRESULT fr;    <span class="c">/* FatFs return code */</span>


    <span class="c">/* Register work area to the default drive */</span>
    f_mount(&amp;FatFs, "", 0);

    <span class="c">/* Open a text file */</span>
    fr = f_open(&amp;fil, "message.txt", FA_READ);
    if (fr) return (int)fr;

    <span class="c">/* Read all lines and display it */</span>
    while (f_gets(line, sizeof line, &amp;fil))
        printf(line);

    <span class="c">/* Close the file */</span>
    f_close(&amp;fil);

    return 0;
}
</pre>
<pre>
<span class="c">/* Copy a file "file.bin" on the drive 1 to drive 0 */</span>

int main (void)
{
    FATFS fs[2];         <span class="c">/* Work area (file system object) for logical drives */</span>
    FIL fsrc, fdst;      <span class="c">/* File objects */</span>
    BYTE buffer[4096];   <span class="c">/* File copy buffer */</span>
    FRESULT fr;          <span class="c">/* FatFs function common result code */</span>
    UINT br, bw;         <span class="c">/* File read/write count */</span>


    <span class="c">/* Register work area for each logical drive */</span>
    f_mount(&amp;fs[0], "0:", 0);
    f_mount(&amp;fs[1], "1:", 0);

    <span class="c">/* Open source file on the drive 1 */</span>
    fr = f_open(&amp;fsrc, "1:file.bin", FA_READ);
    if (fr) return (int)fr;

    <span class="c">/* Create destination file on the drive 0 */</span>
    fr = f_open(&amp;fdst, "0:file.bin", FA_WRITE | FA_CREATE_ALWAYS);
    if (fr) return (int)fr;

    <span class="c">/* Copy source to destination */</span>
    for (;;) {
        fr = f_read(&amp;fsrc, buffer, sizeof buffer, &amp;br);  <span class="c">/* Read a chunk of source file */</span>
        if (fr || br == 0) break; <span class="c">/* error or eof */</span>
        fr = f_write(&amp;fdst, buffer, br, &amp;bw);            <span class="c">/* Write it to the destination file */</span>
        if (fr || bw &lt; br) break; <span class="c">/* error or disk full */</span>
    }

    <span class="c">/* Close open files */</span>
    f_close(&amp;fsrc);
    f_close(&amp;fdst);

    <span class="c">/* Unregister work area prior to discard it */</span>
    f_mount(NULL, "0:", 0);
    f_mount(NULL, "1:", 0);

    return (int)fr;
}
</pre>
</div>


<div class="para ref">
<h4>See Also</h4>
<p><tt><a href="read.html">f_read</a>, <a href="write.html">f_write</a>, <a href="close.html">f_close</a>, <a href="sfile.html">FIL</a>, <a href="sfatfs.html">FATFS</a></tt></p>
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